The present invention relates to an optical information transmission technology and, more specifically, to a connector for transmitting optical information between semiconductor devices, and to an optical waveguide alignment method.
The information processing speed of information processing devices such as computers has improved in recent years. However, as the quantities and types of information to be processed have increased, so have demands for further improvement in the processing speed of these information processing devices. Optical communication is able to handle large amounts of information transmission, and higher density packaging without adverse effects such as parasitic capacitance is anticipated. Therefore, silicon photonics devices have been proposed to convert electronic information signal into optical information signal for transmission.
Silicon photonics devices use optical fibers and waveguides such as planar waveguides to transmit information between devices. Various semiconductor devices using optical waveguides have been proposed. For example, a connector able to couple a wafer to an optical fiber has been proposed in U.S. Pat. No. 8,534,927 (Patent Literature 1) which includes a flexible cladding layer mounted on a support, and single-mode waveguides mounted on top of the cladding layer. U.S. Pat. No. 8,545,108 (Patent Literature 2) describes the coupling of a semiconductor device to a single-mode optical fiber by affixing a “body portion” to a wafer.
Japanese Laid-open Patent Application No. 2007-272159 (Patent Literature 3) describes a waveguide having an alignment core coming into contact with a portion of a ferrule main body. Japanese Laid-open Patent Application No. 2008-089879 (Patent Literature 4) describes a positioning portion formed by patterning the thin film used to form overcladding. Japanese Laid-open Patent Application No. 2005-292379 (Patent Literature 5) describes the positioning and fixing of an optical waveguide to a support using recess-and-protrusion mating.
All of these prior art techniques describe the coupling of a single-mode optical fiber to some type of semiconductor substrate. However, when optical signals are to be transmitted to a silicon photonics device, the optical signals inputted to and outputted from a silicon photonics device have to be coupled to a single-mode fiber bundle or waveguide bundle providing optical wiring. FIG. 6 shows conventional optical coupling between a silicon photonics device and a single-mode optical fiber bundle.
As shown in FIG. 6, an optical coupling is provided between a silicon wafer and a planar waveguide using an adiabatic optical coupling mechanism 620 via a coupling area formed on the output side of the silicon photonics device 610. The waveguide bundle is optically coupled using a polymer ribbon 630. The opposite end of the polymer ribbon 630 is held by a connector 640 or integrally formed with the polymer ribbon 630. The connector 640 holds the polymer ribbon 630 and is optically coupled to the optical output port of a silicon photonics device.
FIG. 7 shows the cross-sectional structure of an optical output unit of a silicon photonics device 610 of the prior art. As shown in FIG. 7, the optical output unit of the silicon photonics device 610 is formed with silicon waveguides 710, and optical signals are coupled to the waveguides 730 formed in the polymer ribbon 720 via suitable coupling devices (not shown). The silicon waveguides 710 are formed in a silicon substrate using any thin-film or photolithographic technique common in the art.
The coupling devices connect a silicon photonics device 610 or optical signals from an external device to optical waveguides 730 and a silicon photonics device 610.
As shown in FIG. 7, alignment ridges 740 are formed on both sides of the polymer ribbon 720. Grooves 760 are formed in the silicon photonics device 610 in positions corresponding to the ridges 740, and the single-mode optical waveguides 730 and silicon waveguides 710 are positioned with respect to each other using these ridges and grooves.
While there have been various disclosures of the technology described above for positioning optical waveguides on a silicon wafer, the research on connectors that hold optical waveguides with precision in order to transmit optical information signals between silicon photonics devices has been anything but sufficient. Most connectors are made of a polymer material, and polymer ribbons are made of a suitably flexible polymer material. However, these polymer materials have insufficient dimensional precision in terms of thickness, width, etc. compared to inorganic materials even when thermosetting resins are used.
Also, when a plurality of waveguides are arranged side-by-side in a polymer ribbon 720, each of these waveguides has to be positioned with precision relative to the connector. In other words, a connector and alignment method are needed to be able to precisely align a polymer ribbon with a silicon photonics device.